An image forming apparatus, e.g., a printer, which is configured to print images on both sides of a sheet, is known.
The printer is configured to change a status of the sheet between when the sheet is ejected from the main body of the printer and stacked and when the sheet is fed back into the main body.
Specifically, the printer includes a corrugation protrusion and a corrugation changing mechanism, which are disposed in proximity to a sheet ejection port. The corrugation protrusion protrudes toward a sheet feed path to corrugate the sheet passing through the sheet feed path. The corrugation changing mechanism is configured to move the sheet feed path such that an amount of the corrugation protrusion protruding toward the sheet feed path varies. When a sheet is ejected from the main body, the corrugation changing mechanism causes the corrugation protrusion to protrude toward the sheet feed path to contact the sheet such that the sheet is corrugated to have increased stiffness. Thus, the sheet can be prevented from being ejected while being curled and the ejected sheet can be stacked neatly. The stiffness of a sheet is a force of the sheet to maintain its original state without bending easily, that is, the tension of the sheet. When the sheet is feed back into the main body, the corrugation changing mechanism changes a feed path of the sheet to be fed such that the sheet does not contact the corrugation protrusion, in other words, the sheet is not corrugated or not given stiffness. This structure reduces, in a path for printing a second side of a sheet, noise caused by contact of the sheet to the main body and damage to the sheet slidingly contacting the main body.